The correct name for this item is "Rope, Drag,
with Shoulder-Strap, M-1918." It was used for pulling artillery
pieces, etc and was not a mountain troop item. The 1918 in the name
makes it clear that these straps predate the creation of the mountain
troops by twenty-four year.

This type of strap has appeared on the internet multiple
times under a variety of names and is often described as mountain troop
equipment, usually in some way related to pulling sleds. In this case
the seller described it as " a pair of 42 dated toggle straps
used by mountain troops and engineers to lug or carry gear".